This invention relates to an apparatus and method for use in the manufacture of magnetic reed contact units.
British Pat. No. 1,464,406 describes the assembly of a magnetic reed contact unit during which the upper magnetic reed is held in a clamp while the lower magnetic reed is supported solely by magnetic attraction from the upper reed across the air gap of a magnetic circuit. In order to align the remote end of the lower reed, a magnetic pin forms one pole of the magnetic circuit and thus localizes magnetic influence on the remote end of the lower reed to align the lower end very accurately with the tip of the pin.
With the advent of a longer magnetic reed contact unit, we tried to modify our existing equipment by shortening the length of the magnetic pin but without success. We believe the shorter pin was not localizing the magnetic influence sufficiently with the result that the alignment of the lower reed could not always be guaranteed.
Various other arrangements have been proposed to align the overlapped reeds, including British Pat. No. 1,013,913 which has clamps for supporting both the upper and lower reeds and British Pat. No. 1,106,379 which shows gripping jaws which hold the reeds. In both cases one reed is eventually magnetically supported from the other reed and during the magnetic supporting, no further alignment mechanism is utilized to maintain the reeds in axial alignment. All these arrangements are relatively complicated or do not guarantee good alignment particularly during the critical sealing process when the reeds are sealed through the ends of the glass envelope.